What if nuclear energy offered the world the only chance to escape poverty and control global warming?

A documentary that lends a pulpit to former opponents of nuclear energy who have made a 180-degree turn has made a splash at the Sundance Film Festival.

The film, titled "Pandora's Promise" and produced by Anglo-American director Robert Stone, was presented Friday at the independent film event, which runs until January 27 in this mountain city in Utah.

Stone, whose anti-nuclear film "Radio Bikini" (1988) was nominated for an Oscar for best documentary, has long been a bitter opponent of atomic energy.

But his positions have evolved as he produced "Earth Days" (2009), a history of the US environmental movement.

"I really discovered there was a lot of cynicism and fatalism and apocalyptic thinking on the part of most of the environmentalists," Stone told AFP. "They really didn't think that their solutions would ever going to work, and we were really all doomed. I don't want to think that way."

"Pandora's Promise" offers an opportunity to speak to leading scientists, environmentalists, scientists, activists and journalists, who had been fiercely anti-nuclear most of their lives, but then changed their minds.

"I wanted the film to be told through the eyes of people who were anti-nuclear and changed their minds," the director said. "And I wanted to have them address why they were anti-nuclear."

The film does not portray nuclear energy as perfect. But it takes a pragmatic stance, seeking to tear down -- statistics in hand -- some ideas supported by the environmental movement, such as achieving robust economic growth while consuming less energy.

One of the participants in the documentary notes that an iPhone -- and the computer servers that run its applications -- together consume as much electricity as a refrigerator.

"It's a fact, we are here," noted Stone. "We are not going anywhere, there's more of us, and I think we have a moral obligation to lift the rest of the world out of poverty and not just leave them behind. And in order to do that, we will need a lot more energy."

Stone believes there is a need to break what he calls "this fantasy that first of all we're going to power the world with wind and solar" energies.

"And I don't put much faith in the whole world agreeing on limiting greenhouse gases," he argued. "I think the future is going to be in designing very simple effective advanced nuclear reactors."

He spoke of the need to minimize the human impact on the planet.

"And the only way to do that is not scaling back and going back to the 19th century," he said. "It's using the best technology we have."

"Pandora's Promise" addresses the fears of nuclear power, including the risk of accidents.

The film begins with images of the 2011 Fukushima nuclear plant accident in Japan, of nuclear weapons proliferation and challenges posed by nuclear waste.

Using documents, including those from the United Nations, it seeks to make the risks of nuclear power relative to those posed by the use of fossil fuels.

The documentary states that nuclear energy remains today the cleanest and least dangerous of all.

According to Stone, the number of environmentalists reconsidering the value of nuclear energy is now increasing.

"We are at a tipping point," he said. "We know now that 2012 was the hottest year ever. Hurricane Sandy, I think, has woken up a lot of people up, people are realizing that the things that we've been doing are not working and we have to do something else. Nuclear is that thing, but people have been afraid to go there."